Cobalt-based bimetallic Prussian blue analogues modified with Selenization and carbon coating as high-performance...

Prussian blue analogues (PBAs) are widely recognized as versatile precursors for designing high-performance anode materials in sodium-ion batteries (SIBs), but their application is restricted by poor conductivity and severe volume variation. Selenization generates metal selenides with superior electrical conductivity and richer redox chemistry, while polydopamine (PDA)-derived carbon coating provides nitrogen-doped carbon frameworks that stabilize the structure and facilitate charge transport. In this work, cobalt-based PBAs with secondary metals including Mn, Zn, Fe, and Ni are synthesized and systematically compared as the anode materials of SIBs. Among them, cobalt-iron PBA (CoFe PBA) exhibits the highest initial capacity of 1054.4 mAh/g at 0.05 A/g but suffers from rapid fading. Post-synthetic modification through combined selenization and carbon coating (CoFe/Se/NC) markedly improves electrochemical behavior, delivering reversible capacities of 782.1 and 514.1 mAh/g respectively at the first and second cycles, and retaining 421.5 and 323.9 mAh/g respectively at 0.1 and 1.0 A/g after 100 cycles. The enhanced sodium ion diffusion coefficient of CoFe/Se/NC confirms accelerated ion transport and favorable reaction kinetics. This study establishes clear correlations between composition, surface modification, and sodium-storage performance, demonstrating the effectiveness of compositional engineering and hybrid structural design in developing PBAs as competitive anode materials for next-generation SIBs.